Universal Phase Dimming Module

ABSTRACT

A universal load control module may include a power supply that operates over a wide voltage range, a microcontroller, and one or more functional control blocks. A functional control block may include a dimmer circuit for controlling a lighting load that provides reverse phase cut mode dimming, forward phase cut mode dimming, and hybrid phase cut mode dimming, as well as thermal protection. One or more universal control modules may be housed in a cabinet that include a cabinet control module. The cabinet may include additional thermal protection measures.

RELATED APPLICATIONS

The present application claims priority to U.S. provisional applicationNo. 61/813,456 for “Multi-Volt Dimmer Cabinet” filed Apr. 18, 2013,which is incorporated by reference herein in its entirety. The presentapplication is related to U.S. Ser. Nos. ______ (attorney docket nos.N0023/903610, N0023/903611, and N0023/903612) filed concurrentlyherewith.

FIELD OF THE INVENTION

The present invention is directed to a lighting control system thatprovides dimming and that operates over a wide input voltage range.

BACKGROUND

Dimmer circuits and dimmer cabinet assemblies currently offered in themarket are typically specific to the voltage of the power circuit sincemany of the main components of the dimmer circuit are designed tooperate at a specific voltage or a very narrow voltage range. As aresult manufacturers, distributors, and retailers need to produce andstock multiple versions of dimmer circuits and dimmer cabinetassemblies. They also need to make sure that the correct dimmer circuitor dimmer cabinet assembly is provided to their customer. It would besimpler if a single dimmer circuit or a single dimmer cabinet assemblycould operate over a wider voltage range because it would minimize thenumber of different dimmer circuits and dimmer cabinet assembliesrequired and would reduce the possibility of filling an order with theincorrect product.

SUMMARY

The present invention is directed to a lighting control system and itscomponents configured to operate across a wide range of input voltagesor across multiple ranges of input voltages.

One aspect of the invention is directed to a dimmer circuit thatprovides reverse phase cut mode dimming, forward phase cut mode dimming,and hybrid phase cut mode dimming. The dimmer circuit may includetransition time control, over current protection, and inductive loadsensing. Thermal protection for the module may be provided through acombination of physical components and firmware.

Another aspect of the invention is a universal load control module. Theuniversal load control module may combine functional control blocks,such as a dimmer circuit, a control interface and/or a communicationsinterface, along with a microcontroller and a power supply that canoperate across a wide voltage range.

In yet another aspect of the invention, a cabinet houses multipleuniversal load control modules. The cabinet may include a cabinetcontrol module, which configures and controls the modules, as well asprovides an external interface. The cabinet may also include features toassist with thermal protection, such as a thermal shelf, spaced apartbranch circuit breakers and an optional cooling device.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of the presentdisclosure are better understood when the following Detailed Descriptionis read with reference to the accompanying drawings, where:

FIG. 1 is a block diagram of an exemplary universal phase dimmingmodule.

FIG. 2 is a block diagram of an exemplary universal power supply.

FIG. 3 is a circuit diagram of an exemplary zero cross detectioncircuit.

FIG. 4 illustrates an output of the exemplary zero cross detectioncircuit of FIG. 3.

FIG. 5 is a circuit diagram of an exemplary dimmer circuit.

FIG. 6 illustrates reverse phase cut mode dimming for an exemplarydimmer.

FIG. 7 illustrates forward phase cut mode dimming for an exemplarydimmer.

FIG. 8 is a circuit diagram of an exemplary dimmer withtemperature-based slew rate control.

FIG. 9 is a circuit diagram of an exemplary dimmer circuit withmultistage transitional control.

FIG. 10 is a block diagram of an exemplary current sense device.

FIG. 11 is a circuit diagram of an exemplary dimmer circuit withinductive load sensing.

FIG. 12 illustrates an output of the exemplary inductive load sensingcircuit of FIG. 11.

FIG. 13 illustrates hybrid phase cut mode dimming for an exemplarydimmer.

FIG. 14 is a block diagram of an exemplary universal load controlmodule.

FIG. 15 is a front view of an exemplary load control cabinet without itsfront panel.

FIG. 16 is a front view of a front panel of an exemplary load controlcabinet.

FIG. 17 illustrates the arrangement of branch circuit breakers in anexemplary load control cabinet.

FIG. 18 illustrates the placement of a main circuit breaker in anexemplary load control cabinet.

FIG. 19 illustrates a thermal shelf in an exemplary load controlcabinet.

DETAILED DESCRIPTION

The present invention is directed to a lighting control system and itscomponents, and in particular to a dimmer circuit, a load control modulethat may include the dimmer circuit, and a load control cabinet that mayinclude the module. The system and its components are configured tooperate across a wide range of input voltages or across multiple rangesof input voltages. The system may provide multiple dimmers and includethermal protection. A load control module may include one or moredimmers and/or a control or communication interface. A cabinet assemblymay include multiple load control modules controlled by a cabinetcontrol module. Alternatively, a single load control module may beconfigured to operate in a stand-alone mode.

The system and/or its components may be referred to as “universal” or“multi-volt” since they can operate over a wide range of input voltagesor over multiple ranges of input voltages. Typically, the system doesnot require user intervention to configure the system or its componentsto any particular input voltage. Instead, the components of the systemautomatically adjust to the input voltage. In an exemplary lightingcontrol system, the input voltage may be 120/230/277 Vac, 50/60 Hz.Other systems may operate with different input voltages, includingvoltages up to at least 347 Vac.

One aspect of the invention is a dimmer circuit. The dimmer circuit mayinclude circuitry to support reverse phase cut mode dimming, forwardphase cut mode dimming, and hybrid phase cut mode dimming. The dimmermodule may also include ON/OFF and slew rate control, wave shaping,transition time control, over current protection, and inductive loadsensing. Thermal protection for the module may be provided through acombination of physical components and firmware.

Another aspect of the invention is a universal load control module. Theuniversal load control module may combine functional control blocks,such as a dimmer, 0-10V control, a DALI interface, etc. in a singlemodule. The universal load control module may operate independently ormay be controlled with other universal load control modules by a cabinetcontrol module.

In yet another aspect of the invention, a cabinet houses multipleuniversal load control modules. The cabinet may include a cabinetcontrol module, which configures and controls the modules, as well asprovides an external interface.

Universal Phase Dimming Module

FIG. 1 is a block diagram illustrating an exemplary universal phasedimming module that operates over multiple voltage ranges. The universalphase dimming module includes a power supply 102, a zero cross detectioncircuit 104, a microcontroller 120, optional relay and relay controlcircuitry 130, 131, power switching devices 110, 111, ON/OFF and slewrate control circuitry 108, 109, inductive load sense circuitry 112,113, current sense circuitry 106, 107, and temperature sense circuitry122. Although FIG. 1 illustrates an embodiment that supports two dimmers(dimmer #1, dimmer #2) connected to two loads (LOAD #1, LOAD #2), otherembodiments may support a different number of dimmers and loads. Thedimmer circuit may be configured for forward phase cut (FPC), reversephase cut (RPC) and hybrid phase cut (HPC) operating modes.

A relay and relay control circuitry 130, 131 may be used in a dimmingsystem that uses a three-wire ballast. An electro-mechanical relay maybe placed in series with the dimmer output to provide air gap isolationwhen the dimmer is in the OFF state. In this implementation, the inputsto the three-wire ballast include the output of the relay, the phasecontrol signal output by the dimmer, and neutral. In other applications,the relay and relay control circuitry may not be needed.

FIG. 1 illustrates a signal from the microcontroller to the low powerisolation DC-DC switched mode power supply 141. This signal may be anenable signal or it may be a PWM (pulse width modulation) control signaloutput by the microprocessor. The signal controls the low powerisolation DC-DC switched mode power supply 141 so that it powers downthe dimmer circuitry when the dimmer is OFF. A similar signal may beprovided to the low power isolation block 140 (not shown). Inapplications that are not efficiency sensitive in the OFF state, thesignal from the microcontroller may not be needed.

The microcontroller 120 outputs the PWM control signal to the isolatedcommunication block 142, 143. The isolated communication block includesan isolated coupler, such as an optocoupler, digital isolator, or amagnetic coupler. The microcontroller varies the duty cycle of the PWMcontrol signal to control the phase control signal output by the dimmer.

The microcontroller may include computer-readable memory or it mayaccess external computer-readable memory that includescomputer-executable instructions for lighting control, includingdimming. The instructions may be related to lighting control, such asdimmer curves, rooms and zones, time scheduling, or may be related tothermal control. The microcontroller may also receive one or more inputsthat direct the microcontroller to control the dimmer based on thereceived input. The inputs may come directly from a user or through anintervening interface, such as that provided by a cabinet controlmodule.

Power Supply

The dimmer circuit includes a switched mode power supply (SMPS) which iscompatible with a wide input voltage range, e.g., 120/277 Vac, 50/60 Hz.FIG. 2 illustrates one implementation of a power supply 102 thatprovides 24V and 3.3V DC outputs to the remainder of the control anddimmer circuit. The power supply automatically detects the input voltageand adjusts its operations as needed to provide a regulated outputvoltage without requiring user intervention. Other power supplies may beused so long as they have the ability to work across multiple voltageranges or a wide voltage range, preferably without requiring userintervention.

Zero Cross Detection Circuit

The zero cross detection circuit 104 is compatible with a wide inputvoltage operating range. An exemplary zero cross detection circuit isshown in FIG. 3 and utilizes high value input resistors, an efficientR-C trigger circuit, and a transistor to drive an isolating optocoupler,which provides isolation for an input to the microcontroller. The outputof the zero cross detection circuit (“out” in FIG. 2) is provided to theinput of the microcontroller.

The exemplary zero cross detection circuit differs from conventionaldesigns which use simple current limiting resistors to drop the inputvoltage into the isolating optocoupler. Conventional designs balancepower loss and heat in the resistors with the input current requirementsfor the optocoupler, and this balancing exercise precludes its use overa wide input voltage range, since the resistors which provide enoughcurrent at lower voltages dissipate too much power for long-termreliability at the higher voltages. Other conventional designs mayinclude comparators, op amps, 555 timers or inexpensive microcontrollersthat all require a low power universal input power supply to provide aregulated low voltage signal/power to digital and/or analog electronics.

In the exemplary zero cross detection circuit of FIG. 3, the universalinput waveform is sampled with the voltage divider network (R1, R2, R3),energy is stored in capacitor (C1) and the stored energy is releasedthrough the optocoupler and current limiting resistor (R4) when thesampled signal is less than approximately 14.3 V on the base of thetransistor (Q1). The output pulse on the isolated side of theoptocoupler corresponds to the zero crossing of the sampled AC inputvoltage. This simplified comparator functionality doesn't require aconstant or regulated power supply. Therefore, the reliability andexpected lifetime of the circuit is significantly improved while stillproviding a low cost solution. The component values illustrated in FIG.3 are exemplary. Other values, as well as other zero cross detectioncircuits may be used.

FIG. 4 shows the output pulses corresponding to the zero cross points onthe input power-line AC voltage (hot to neutral). The signals would besimilar for other inputs (e.g., 120 Vac-277 Vac) received on theuniversal input. The microcontroller uses the zero-crossing informationfrom the zero cross detection circuit to synchronize its internal timerwith the 60/50 Hz input power. This allows the microcontroller toprovide a PWM control signal synchronized with the input power, whichresults in smooth and flicker-free dimming performance.

Although a zero cross detection circuited is needed for a phase dimmer,circuit designs other than that illustrated in FIG. 2 may be used.

Power Switching Devices

Conventional dimmers may use power switching devices, thyristors such asSilicon Controlled Rectifiers (SCRs), and/or Triacs. These devicesrequire a “latching current” (typically greater than several milliamps)to allow the devices to continue conducting once triggered. Therequirement for a latching current makes these devices inappropriate foruse with modern efficient lighting loads, such as LEDs, which not onlydraw less current, but also may not draw it consistently enough to keepa thyristor latched.

Additionally, thyristor-based dimmer designs require series inductivefiltering to reduce the EMI emitted from the dimmer, as well as theacoustic noise that the powerline switching can induce in the lamps(commonly referred to as “filament sing”). These types of filters areboth load and voltage dependent, and a filter which is designed for a277 V circuit will not have acceptable performance for smaller loads at120 V.

The dimmer circuit uses power switching devices (110, 111 of FIG. 1; U1,U2 of FIG. 5), such as IGBTs or MOSFETs, which do not require either aminimum latching current or a series inductive filter, to allow thedimmer circuit to operate over a wide range of input voltages.

Transition Control, Including ON/OFF and Slew Rate Control

The dimmer circuit also includes circuitry to control the ON/OFF timeand the slew rate. By controlling the slew rate, the dimmer circuitprovides a constant fall rate di/dt for reverse phase cut dimming (SeeFIG. 6) and constant rise rate di/dt for forward phase cut dimming (SeeFIG. 7). By controlling the slew rate, the voltages across the dimmerload exhibit a similar rate of voltage change (dv/dt). Slew rate controlis important for compliance with the FCC standard for radiated/emittedand conductive noise. A dimmer with slew rate control emitssignificantly fewer harmonics than a dimmer without slew rate control.Slew rate control also eliminates the buzzing noise associated withdimming incandescent bulbs with forward phase cut dimmers.

Conventional forward phase cut dimmers that use Triacs and SCRs requirea relatively large inductor to provide series inductive filtering tocontrol the slew rate of the dimmer. In these designs the slew rate isvariable based on the load current, so the published slew rate is onlyapplicable for specific load test conditions. In the present dimmercircuit, the slew rate is independent of the load current. The negativefeedback components (C1, R7, C2, R8) provide feedback to gates of theMOSFETs (U1, U2) in order to regulate the transition time from an ON toOFF state and vice versa. The negative feedback components are notneeded in implementations that use IGBT power switches since negativefeedback is inherent in IGBT power switches. However, the externalcurrent limiting programming resistors on the gates of the IGBTs arenecessary to control the rise/fall rates.

The dimmer circuit may include circuitry for ON/OFF and slew ratecontrol. The ON/OFF and slew rate control may be combined into a singlefunctional block, as shown by 108 and 109 of FIG. 1.

FIG. 5 illustrates an exemplary ON/OFF and slew rate control circuit504, an exemplary wave shaping circuit 502, and an exemplary dimmeroutput circuit 501. The ON/OFF and slew rate control circuit 504 mayinclude transistors (Q1, M1, M2), as well as other components. Themicrocontroller controls the transistors by providing a PWM controlsignal to the circuit. In one implementation, the PWM control signal isfed to the circuit through an optocoupler or a digital coupler.

The power switching devices, such as the MOSFETs (U1, U2), operate inthe linear mode (or resistive or active region) during the transitionfrom the OFF to ON states and the ON to OFF states. The ON/OFF and slewrate control circuit is one option for decreasing the heat dissipationon the power switching devices during the transition from the OFF to ONstates and the ON to OFF states. The ON/OFF and slew rate controlcircuit reduces heat dissipation by reducing the transition time, orslew rate, between the ON/OFF states. For example, the power switchingdevices dissipate more heat when the transition time is 350 us, thanwhen the transition time is 165 us. Additional options may also be usedto dissipate heat, including a heat sink.

When the dimmer provides reverse phase cut mode dimming, the ON/OFF andslew rate control circuitry controls the transition time (slew rate) atthe falling edge of the phase control signal, as shown in FIG. 6. Whenthe dimmer provides forward phase cut mode dimming, the ON/OFF and slewrate control circuitry controls the transition time (slew rate) at therising edge of the phase control signal, as shown in FIG. 7. The phasecontrol signal corresponds to the PWM control signal from themicrocontroller in that the on time of the waveform corresponds to thepulse width of the PWM control signal.

The wave shaping circuit 502 of FIG. 5 is used in reverse phase cut andhybrid phase cut modes to prevent possible oscillations or stabilityissues with the power switching devices. The wave shaping circuitprovides a hard turn-off after a predetermined time based on the timeconstant of the circuit. In one implementation, the circuit is tuned sothat the predetermined time is 165 us at 50% duty cycle.

During the ON/OFF or OFF/ON transition the power switching devicesoperate in the active/linear region and dissipate significant amounts ofpower resulting in higher operating temperatures. Due to the negativetemperature coefficients of D2 and Q2 (approximately −2 mV/C) in thewave shaping circuit 502, there is a variable negative time constantthat is linearly proportional with the ambient temperature inside thedimmer. As a result, there is nominal turn-off control of the dimmer at25 C ambient temperature and reduced turn-off control at higheroperating temperatures, which provides a first level of thermalprotection for the dimmer.

Thermal Protection

The dimmer circuit may monitor temperature and use the temperature toadjust the operation of the dimmer to provide thermal protection otherthan the nominal turn-off control described in the preceding paragraph.FIG. 8 illustrates one thermal protection option. In FIG. 8 theresistors R2, R3 of FIG. 5 are replaced with thermistors (NTCs) so thatthe slew rate is adjusted based on ambient temperature. In reverse phasecut mode, the wave shaping circuit 802 automatically reduces transitiontime (automatic fold-back) with higher ambient temperature so that thedimmer is turned off faster at higher temperatures. This reduces thepower dissipation across the dimmer and provides dynamic thermalprotection. The actuation time of Q2 is controlled by D2 which isdependent on the ambient temperature. In one embodiment the circuitoperates as follows: at 25 C the wave shaping circuit actuates at 165us, at 50 C it actuates at 125 us, at 75 C at 100 us, etc. When Q2actuates, the gate voltage is pulled to ground and the power switchingdevices (U1, U2 in FIG. 8, 110, 111 in FIG. 1) turn OFF and exit theresistive or active or linear mode of operation.

FIG. 9 illustrates another alternative to FIG. 5. Instead of themicrocontroller controlling the ON/OFF and slew rate circuitry shown inFIG. 5 via the PWM control signal, the microcontroller selects aspecific transition circuit 902, 904 or 906 by providing dual PWMcontrol signals to the selected circuit. The different transitioncircuits provide different transition times. One advantage of themultistage transition control shown in FIG. 9 is that it providesmultiple transition time options, instead of a single transition time(e.g., 165 us at 50% duty cycle), as provided by the single stage ofFIG. 5. FIG. 9 illustrates three transition circuits, 902, 904, 906. Oneof the transition circuits 902 provides a long transition time, e.g.,350 us, a second transition circuit 904 provides a medium transitiontime, e.g., 165 us, and a third transition circuit 906 provides a shorttransition time, e.g., <10 us. The programming resistors (R1, R2, R3)determine the transition timing for each transition circuit. A largervalue will set a longer or slower transition rate, whereas a smallerresistor value will provide a faster or shorter transition rate. Themicrocontroller selects transition circuit 902 using Trans1_ON andTrans1_OFF, selects transition circuit 904 using Trans2_ON andTrans2_OFF, and selects transition circuit 906 using Trans3_ON andTrans3_OFF. For example, when transition circuit 902 is selected, the ontime of the phase control signal is based on the pulse width of the PWMcontrol signal applied to Trans1_ON and the off time of the phasecontrol signal is based on the pulse width of the PWM control signalapplied to Trans1_OFF.

In one embodiment, the microcontroller selects the transition time basedon temperature, such as the ambient temperature or MOSFET temperature.The microcontroller selects the long transition time circuit 902 whenthe dimmer is operating at safe/normal temperatures, selects the mediumtransition time circuit 904 when the dimmer is running hot, and selectsthe short transition time circuit 906 when the ambient temperature isnear the safe operating limits and/or the dimmer is overloaded causinghigh temperatures on the power switches. The short transition timecircuit 906 provides a minimum transition time so that the powerswitching devices operate in the linear region for a shorter time andthus dissipate less power.

In one implementation the microcontroller compares the temperature tostored values or thresholds. If the temperature is below a firstthreshold, then the microcontroller selects the long transition time. Ifthe temperature is between the first threshold and a second threshold,then the microcontroller selects the medium transition time and if thetemperature is above the second threshold, then it selects the shorttransition time.

In an alternative implementation, only one transition circuit with anadjustable resistor. In this implementation, the programming resistor(e.g., R1) is replaced by an adjustable resistor and the differentvalues provide different transition times. For example, the adjustableresistor could be a programmable digital potentiometer with for example64 or 128 taps. Each tap selects a different internal resistor thatprovides a different transition rates (64/128/256/etc.). Alternatively,this could also be accomplished in the analog domain with J-FET, MOSFETor BJT operating in the active/resistive/linear region to have aninfinite number of programmable resistor values. An op amp/comparatorcircuit configuration may be used for setting the programmable resistorvalues.

Although not shown in FIG. 9, a wave shaping circuit such as that shownin FIG. 5, may also be included to support reverse phase cut mode orhybrid phase cut mode dimming.

Additional or alternative thermal protection may be provided by themicrocontroller 120 by controlling the phase angle or duty cycle of thePWM control signal based on temperature. The microcontroller may obtaintemperature information from a temperature sensor 122 of FIG. 1. Thetemperature sensor may be a thermistor, temperature sensor, diode, aninternal temperature sensor on the microcontroller, or any othersuitable sensor. In one example, the ADC value of the measuredtemperature is an input to P/PI/PID(proportional/proportional-integral/proportional-integral-derivative)microcontroller, which may be implemented in firmware on themicrocontroller.

If the ambient temperature in the proximity of power switching devices(or direct temperature measurement on the power devices' packaging)exceeds a temperature threshold for the power switching devices and thephase angle exceeds a phase angle threshold, e.g., greater than 55%,then the microcontroller increases the duty cycle of the PWM controlsignal to decrease the power dissipation on the power switching devicesand therefore slow the temperature rise of the die junction inside thesilicon power switching devices (MOSFETs/IGBTs/etc). If the temperatureis still above the temperature threshold when power switching devicesare at 100% duty cycle, then the microcontroller will control the PWMcontrol signal to provide a 0% duty cycle to turn off the dimmer toprotect it from an over-temperature condition. If the temperatureexceeds the temperature threshold and the phase angle is less than thephase angle threshold, e.g. less than 55%, then the microcontrollerdecreases the duty cycle of the PWM control signal to decrease the powerdissipation on the MOSFETs and therefore lowers the die junctiontemperature within the Safe Operating Area (SOA as specified in thedatasheet from power switching device manufacturer). The P/PI/PIDcontrol algorithm stabilizes the dimmer response and eliminates rapiddimming control fluctuations.

Over Current Protection

The dimmer module of FIG. 1 may include current sense devices 106, 107,such as a current sense transformer, Hall affect sensor, current senseresistor, etc. FIG. 10 illustrates an exemplary Hall affect sensor.

The microcontroller receives an output signal from the current sensedevice via an ADC input, calculates the rms value and measures the peakvalue, and ensures that the maximum rms and peak ratings of the dimmerare not exceeded. The microcontroller determines if the duty cycle ofthe PWM control signal needs to be reduced, or if the dimmer needs to beturned off in order to protect the power switching devices from failure.

Another purpose of the current sense device is to detect if any of thepower switching devices 110, 111 of FIG. 1 failed open or in a shortedcondition. The microcontroller sets the PWM control signal output tomaximum if one device fails short. This prevents possible large loadingunbalance in a single or three phase system. It also disables dimming,which provides an indication to the user of the failure.

Inductive Load Protection

In one implementation, the default dimmer operating mode is reversephase cut dimming. This operating mode avoids the inrush current andresulting buzzing noise when incandescent lamps are dimmed with astandard forward phase cut dimmer. One disadvantage of reverse phase cutdimming is that the current through the load is disrupted abruptly. Thisis not an issue for resistive (current in phase with voltage, e. g.,incandescent/tungsten bulbs) and capacitive (current leading voltage)loads. However, for inductive loads (current lagging voltage) thiscondition could damage the dimmer. Disrupted current flow though theinductive load could create a large flyback voltage and the dimmercircuit will fail if the peak flyback voltage exceeds the maximumvoltage withstand rating of the power switching devices.

The dimmer circuit may also include an inductive sense circuit, as shownin FIG. 1, 112, 113, to detect the flyback voltage. An exemplaryinductive sense circuit 1102 is further illustrated by FIG. 11. Thecircuit includes a comparator, sampling circuit, and reference voltageand generates an output signal that is transmitted through an isolatedcoupling device to the microcontroller, which notifies themicrocontroller that the flyback voltage is present with a peakdangerously close to the maximum voltage rating of the MOSFET. Themicrocontroller determines whether the phase angle needs to be reduced,or the operating mode needs to change from reverse to forward phase cutmode or hybrid phase cut mode where the dimmer is switched off at thecurrent zero cross point.

In one implementation, when the inductive sense circuit 1101 detects adangerously large flyback peak voltage, it sends a pulse or flybackvoltage warning information to the microcontroller. FIG. 12 shows atypical response of the comparator circuit with flyback voltage from theinductive load that exceeds 570 Vpk. The pulse may be sent through anisolated coupling device, such as an optocoupler or magnetic coupler.Once the microcontroller detects the pulse, it stops increasing the dutycycle of the PWM control signal and waits for multiple periodic pulses(50/60 Hz) to validate the input. If the input is validated, then themicrocontroller modifies the PWM control signal to switch from RPC toFPC mode. If the pulses continue while in FPC mode, then themicrocontroller switches from FPC to HPC mode. The microcontrollerincreases the duty cycle in HPC mode until the pulses stop.

Switching the dimmer off at or near the current zero cross pointeliminates the presence of flyback voltage that could damage the dimmer.The current sense circuit (106, 107 of FIG. 1) enables the HPC mode ofoperation in which the microcontroller turns off the dimmer near thecurrent zero cross point. FIG. 13 illustrates the hybrid mode ofoperation.

Universal Load Control Module

A dimmer, such as the universal dimmer circuit described above, may becombined with other circuits or functional blocks in a universal loadcontrol module, also referred to herein as a load control module. In oneimplementation, a universal load control module may include multipleuniversal phase dimmers. In another implementation, a universal loadcontrol module may include a universal phase dimmer and a lightingcontrol module that provides ON/OFF switching/relay lighting control. Inyet another implementation, a universal load control module may includea universal phase dimmer and a functional control block that provides acontrol interface such as a 0-10V control interface, or a communicationinterface such as a DALI, RS242, DMX, DMX/RDM, CAN, USB, I2C, or SPIinterface or a wireless interface such as a WIFI (IEEE 802.11),Bluetooth (IEEE 802.15.1), or ZIGBEE (IEEE 802.15.4) interface. Otherimplementations may include other combinations of functional blocks. Theinputs and outputs of the universal load control module depend upon therequirements of the functional control blocks. For example, if afunctional control block provides ON/OFF switching load control, thenthe functional control block may include outputs that control relays,solenoids or SSR (Solid State Relays) to control the load, where theload may include lighting fixtures, fans, HVAC, motors, etc. Therelays/solenoids/SSR are turned off when power to the load is are notneeded, for example, during the night or weekends when the building orworkspace is not occupied.

The architecture of the universal load control module is illustrated byFIG. 14. The universal load control module 1400 includes a power supply1406, a microcontroller 1408, and one or more functional control blocks1402, 1404. Each functional control block may include its own isolatedpower supply block 1410, 1412 and each functional control block operatesindependently of any other functional control block in the universalload control module.

The power supply blocks 1410, 1412 may include a low power flybackconverter. The flyback converters may be powered from a 24V, 3.3V or anyother low voltage output available from the power supply 1406 ordirectly from the line voltage (120/230/277/347 Vac 50/60 Hz). The powersupply blocks provide isolation between high voltage and low voltage.The function provided by the power supply blocks is similar to thefunction provided by the low power isolation DC-DC SMPS block in FIG. 1.Some functional control blocks may not require a power supply block, sothe blocks are shown in dashed lines in FIG. 14. For example, if afunctional control block includes a communication or control interface,then the power supply block may not be needed. However, it is includedwhenever there is a need to isolate high and low voltages.

One benefit of the isolated functional control blocks is that a fault ormis-wire on one input/output terminal does not propagate to otherfunctional control blocks within the control module or to the rest ofthe system. Another advantage of the modular design of the universalload control module is that it allows mixing and matching of functionalblocks to support a wide range of applications.

A universal load control module may also include an optional zero crossdetection circuit 1407. The zero cross detection circuit may be includedwhen at least one of the functional control blocks includes a phasedimmer or a switching ON/OFF control.

If a universal phase dimmer circuit is included as a functional controlblock in a universal load control module, then a dimmer circuit similarto that illustrated in FIG. 1 may be included in one of the functionalcontrol blocks. Since the universal load control module may include apower supply 1406, a zero cross detection circuit 1407, and amicrocontroller 1408, the dimmer circuit can use these components, i.e.,the functions for microcontroller 120 described above may be performedby microcontroller 1408, etc.

Another functional control block in the universal load control modulemay provide a lighting communication interface, such as a DALIinterface. A universal load control module configured in this manner mayoperate independently or may be part of a larger system. If theuniversal load control module operates independently, it may use its ownmicrocontroller, such as microcontroller 1408, for configuring thedimmer and for providing an external interface or it may rely on anexternal microcontroller. In the example with a DALI interface, the loadcontrol module may interact with a remote DALI controller via its DALIinterface.

Other implementations of the universal load control module may notinclude a phase dimmer or may provide a different type of control orcommunication interface. For example, a functional control block mayprovide a communication interface to a cabinet control module or anexternal controller. If a universal control module only includes controland/or communication interfaces, then it may also be referred to as auniversal control module. In addition, the universal load control moduleis not limited to two functional control blocks. A functional controlblock may be configured for wired or wireless communication and maysupport communication standards including, but not limited to ZIGBEE,WIFI, or Bluetooth standards.

Universal Load Control Cabinet

Multiple universal load control modules may be mounted in a singlecabinet. FIG. 15 illustrates one implementation of a cabinet 1500 thatcan accommodate up to six universal load control modules 1502-1512. Eachcontrol module is connected to a terminal block, such as terminal block1522 (for simplicity only one of the six terminal blocks is labeled inFIG. 15). The terminal blocks connect the modules to the power wireharness 1530 that carries a set of conductors that provides power to themodules. The cabinet also includes a ground distribution bar 1526, anoptional neutral distribution bar 1524, an optional 3-phase distributionblock 1518, branch circuit breakers 1520, a communication wire harness1514, and a cabinet control module 1516. The communication wire harness1514 carries a set of conductors that connects the cabinet controlmodule 1516 to the universal load control modules 1502-1512.

Alternative designs of the cabinet may support different numbers ofuniversal load control modules. For example, a small cabinet may supportup to 3 universal load control modules, a medium cabinet may support upto 6 modules, and a large cabinet may support up to 9 modules.

FIG. 16 illustrates the front panel of 1600 of the cabinet andillustrates venting 1602 in the area of the universal load controlmodules and an access panel 1604 to access the branch circuit breakers1520 and an optional cabinet control module.

Since multiple universal load control modules may be mounted in the samecabinet, the cabinet may provide multiple branch circuit breakers. Inone implementation, the branch circuit breakers are universal input(i.e., multi-volt) thermal magnetic circuit breakers, such as thoseoffered by EATON, part number: FAZ-D20/1-NA-SP. The branch circuitbreakers are mounted in the cabinet so that there is an air-gap betweenthe breakers. This spacing allows the breakers to operate over theirfull input current range without de-rating. FIG. 17 shows an exemplaryarrangement of the breakers. As shown in FIG. 15, the breakers may bemounted below the universal load control modules, typically towards thebottom of the panel, so that the performance and ratings of breakers isnot affected by the heat generated in the modules. In a feed throughimplementation, the branch circuit breakers are external to the cabinet.

In addition to the branch circuit breakers, there is a main circuitbreaker. The main circuit breaker is a multi-volt breaker and may belocated in the cabinet or may be external to the cabinet. FIG. 15illustrates a cabinet configuration where the main circuit breaker ismounted outside the cabinet and FIG. 18 illustrates a cabinetconfiguration where the main circuit breaker 1802 is mounted inside thecabinet. If the main circuit breaker is mounted inside the cabinet, thenthe 3-phase distribution block shown in FIG. 15 is not required. Thecabinet may be powered with single, dual or 3 phase (120/230/277/347Vac, 50/60 Hz).

The cabinet may include an optional thermal shelf. FIG. 19 illustrates athermal shelf 1902 located between two adjacent universal load controlmodules. The thermal shelf disrupts the heat flow from the lower modulesto the upper modules and forces the heat to flow away from the modules.The cabinet may further include an active cooling device, such as a fanor synjet (membrane) device(s). In one implementation, the coolingdevice is mounted near the top of the cabinet above the universal loadcontrol modules.

Universal Cabinet Control Module

The universal cabinet control module communicates with the universalload control modules, including the functional control blocks within theuniversal load control modules in the cabinet and communicates withexternal devices or control equipment. In a stand-alone mode, theuniversal cabinet control module provides a user interface that allows auser to configure and control the universal load control modules in thecabinet. In an external control mode, the universal cabinet controlmodule interfaces with an external controller and a user configures andcontrols the universal load control modules in the cabinet using a userinterface provided by the external controller. Configuration and controlof the cabinet includes configuring the operation of the universal loadcontrol modules, such as selecting the dimmer curves, setting the roomsand zones, programming the time scheduling, setting the moduleaddresses, etc. The universal cabinet control module may support one ormore communication protocols, such as RS485, DMX/RDM, etc.

In one implementation of the stand-alone mode, the user interfaceincludes input devices, such as toggle buttons, and a display, such as a7-segment display or LCD screen. In one implementation of the externalcontrol mode, the universal cabinet control module includes a USB portand an external computing device is connected to the cabinet controlmodule via the USB port.

The universal cabinet control module may include two communicationinterfaces. The cabinet control module uses one interface to communicatewith the universal load control modules in the cabinet and uses theother interface to communicate with external devices, including externalcontrollers and programmable external control equipment. The universalcabinet control module may communicate with a variety of externaldevices, such as computers, tablets, controllers, mobile phones, etc.

The universal cabinet control module may provide cabinet level thermalprotection by monitoring the temperature within the cabinet at one ormore locations or receiving temperature information from each of theuniversal load control modules, and based on the temperature informationreceived, instructing one or more of the universal load control modulesto take action, such as adjusting a phase angle or slew rate or turningoff a dimmer.

The cabinet control module may collect error or failure information fromthe individual universal load control modules and report it to a user.Alternatively, if the universal load control module is operating in astand-alone mode or otherwise configured for communication with a user,the universal load control module may report error or failureinformation directly to the user.

The foregoing is provided for purposes of illustrating, explaining, anddescribing aspects of the present invention. Further modifications andadaptations to these examples will be apparent to those skilled in theart and may be made without departing from the scope or spirit of theinvention. Different arrangements of the components depicted in thedrawings or described above, as well as components not shown ordescribed are possible. For example, the component values, dimensions,and timings provided are exemplary and other values may be used. Inaddition, loads other than lighting loads may controlled. Similarly,some features and subcombinations are useful and may be employed withoutreference to other features and subcombinations. Embodiments of theinvention have been described for illustrative and not restrictivepurposes, and alternative embodiments will become apparent to readers ofthis patent. Accordingly, the present invention is not limited to theembodiments described above or depicted in the drawings, and variousembodiments and modifications can be made without departing from thescope of the invention.

What is claimed is:
 1. A dimmer circuit, comprising: a power supply thatoperates over a wide voltage range by detecting an input voltage andadjusting its operation based on the input voltage to provide at leastone output voltage for components of the dimmer circuit, wherein theoutput voltage is independent of the input voltage; a microcontrollerthat is powered by the power supply and that supports reverse phase cut,forward phase cut, and hybrid phase cut dimming modes, wherein themicrocontroller outputs a PWM (pulse width modulation) control signal;an ON/OFF and slew rate control circuit that provides gate drive controlfor a plurality of power switching devices in a dimmer output circuitand transition time control, wherein the microcontroller controls theON/OFF and slew rate control circuit using the PWM control signal; awave shaping circuit, wherein the wave shaping circuit providesadditional transition time control when the dimmer circuit providesreverse phase cut dimming or hybrid phase cut dimming; and the dimmeroutput circuit that powers a load based on the PWM control signal, thetransition time control provided by the ON/OFF and slew rate controlcircuit, and the additional transition time control provided by the waveshaping circuit, wherein the dimmer output circuit includes MOSFET orIGBT power switching devices.
 2. The dimmer circuit of claim 1, furthercomprising: a zero cross detection circuit that operates over the widevoltage range and that provides an input to the microcontroller thatindicates zero cross points of the input voltage, wherein themicrocontroller uses the input to synchronize the PWM control signal. 3.The dimmer circuit of claim 1, wherein the ON/OFF and slew rate controlcircuit includes at least one thermistor.
 4. The dimmer circuit of claim1, further comprising: a current sense device that senses currentthrough the load and provides load current information to themicrocontroller, wherein the microcontroller is further operable foradjusting a duty cycle of the PWM control signal based on an rms valueand peak current information.
 5. The dimmer circuit of claim 1, furthercomprising: an inductive load sense circuit that senses a flybackvoltage from the load and provides flyback voltage warning informationto the microcontroller, wherein the microcontroller uses the flybackvoltage warning information to determine whether to change a dimmingmode from reverse phase cut to forward phase cut or from forward phasecut to hybrid phase cut.
 6. The dimmer circuit of claim 1, furthercomprising: a temperature sense device that provides temperatureinformation to the microcontroller, wherein the microcontroller isfurther operable for adjusting a duty cycle of the PWM control signalbased on the temperature information.
 7. A dimmer circuit, comprising: apower supply that operates over a wide voltage range by detecting aninput voltage and adjusting its operation based on the input voltage toprovide at least one output voltage for components of the dimmercircuit, wherein the output voltage is independent of the input voltage;a microcontroller that is powered by the power supply and that supportsreverse phase cut, forward phase cut, and hybrid phase cut dimmingmodes, wherein the microcontroller outputs a PWM (pulse widthmodulation) control signal; a first transition circuit that provides afirst transition time; a second transition circuit that provides asecond transition time; wherein the microcontroller selects either thefirst transition circuit or the second transition circuit as a selectedtransition stage circuit to control a transition time; and a dimmeroutput circuit that provides an output to a load based on the PWMcontrol signal and the selected transition circuit, wherein the dimmeroutput circuit includes a plurality of power switching devices operableover the wide voltage range.
 8. The dimmer circuit of claim 7, furthercomprising: a zero cross detection circuit that operates over the widevoltage range and that provides an input to the microcontroller thatindicates zero cross points of the input voltage.
 9. The dimmer circuitof claim 7, further comprising: a current sense device that sensescurrent through the load and provides current information to themicrocontroller, wherein the microcontroller is further operable foradjusting a duty cycle of the PWM control signal based on an rms valueand peak current information.
 10. The dimmer circuit of claim 9, whereinthe current sense device is further operable to detect a failure of oneof the power switching devices and to provide failure information to themicrocontroller, wherein the microcontroller is further operable foradjusting the duty cycle of the PWM control signal to 100% based on thefailure information.
 11. The dimmer circuit of claim 7, furthercomprising: an inductive load sense circuit that senses a flybackvoltage from the load and provides flyback voltage warning informationto the microcontroller, wherein the microcontroller uses the flybackvoltage warning information to determine whether to change a dimmingmode from reverse phase cut to forward phase cut or from forward phasecut to hybrid phase cut.
 12. The dimmer circuit of claim 7, furthercomprising: a temperature sense device that provides temperatureinformation to the microcontroller, wherein the microcontroller isfurther operable for adjusting a duty cycle of the PWM control signalbased on the temperature information.
 13. The dimmer circuit of claim 7,further comprising: a wave shaping circuit, wherein the wave shapingcircuit provides additional transition time control when the dimmercircuit provides reverse phase cut dimming or hybrid phase cut dimming.14. A dimmer circuit, comprising: a power supply that operates over awide voltage range by detecting an input voltage and adjusting itsoperation based on the input voltage to provide at least one outputvoltage for components of the dimmer circuit, wherein the output voltageis independent of the input voltage; a microcontroller that is poweredby the power supply and that supports reverse phase cut, forward phasecut, and hybrid phase cut dimming modes, wherein the microcontrolleroutputs a PWM (pulse width modulation) control signal; an ON/OFF andslew rate control circuit that provides gate drive control for aplurality of power switching devices in a dimmer output circuit andtransition time control, wherein the microcontroller controls the ON/OFFand slew rate control circuit using the PWM control signal; a waveshaping circuit, wherein the wave shaping circuit provides additionaltransition time control when the dimmer circuit provides reverse phasecut dimming or hybrid phase cut dimming; and the dimmer output circuitthat powers a load based on the PWM control signal, the transition timecontrol provided by the ON/OFF and slew rate control circuit, and theadditional transition time control provided by the wave shaping circuit,wherein the dimmer output circuit includes the plurality of powerswitching devices, which are operable over the wide voltage range. 15.The dimmer circuit of claim 14, wherein the ON/OFF and slew rate controlcircuit includes at least one thermistor.
 16. The dimmer circuit ofclaim 14, further comprising: a current sense device that senses currentthrough the load and provides current information to themicrocontroller, wherein the microcontroller is further operable foradjusting a duty cycle of the PWM control signal based on an rms valueand peak current information.
 17. The dimmer circuit of claim 16,wherein the current sense device is further operable to detect a failureof one of the power switching devices and to provide failure informationto the microcontroller, wherein the microcontroller is further operablefor adjusting the duty cycle of the PWM control signal to 100% based onthe failure information.
 18. The dimmer circuit of claim 14, furthercomprising: an inductive load sense circuit that senses a flybackvoltage from the load and provides flyback voltage warning informationto the microcontroller, wherein the microcontroller uses the flybackvoltage warning information to determine whether to change a dimmingmode from reverse phase cut to forward phase cut or from forward phasecut to hybrid phase cut.
 19. The dimmer circuit of claim 14, furthercomprising: a temperature sense device that provides temperatureinformation to the microcontroller, wherein the microcontroller isfurther operable for adjusting a duty cycle of the PWM control signalbased on the temperature information.
 20. The dimmer circuit of claim14, wherein the dimmer circuit is operable to provide inputs to athree-wire ballast or driver, further comprising: a relay controlled bythe microcontroller, wherein an output of the relay is connected to afirst input of the three-wire ballast or driver and an output of thedimmer output circuit is connected to a second input of the three-wireballast or driver.